Makibishi

The term makibishi (撒き菱 or 撒菱) refers to the Japanese version of the caltrop.

The tool (igadama) is a sharp spiked object that was used in feudal Japan to slow down pursuers and also was used in the defense of samurai fortifications.

The term makabishi literally means "scattered water chestnut" in Japanese.

[3] Both types of makibishi could penetrate the thin soles of the shoes such as the waraji sandals that were commonly worn in feudal Japan when the makibishi was dropped on the ground or planted in advance.

[7] Modifications made by the ninja included serrated tips, which were also said to be occasionally coated with poison.